Rational design principles for giant spin Hall effect in 5d -transition metal oxides

Abstract

Spin Hall effect (SHE), a mechanism by which materials convert achargecurrent into aspincurrent, invokes interesting physics and promises to empower transformative, energy-efficient memory technology. However, fundamental questions remain about the essential factors that determine SHE. Here, we solve this open problem, presenting a comprehensive theory of five rational design principles for achievinggiantintrinsic SHE in transition metal oxides. Arising from our key insight regarding the inherently geometric nature of SHE, we demonstrate that two of these design principles are weak crystal fields and the presence of structural distortions. Moreover, we discover that antiperovskites are a highly promising class of materials for achieving giant SHE, reaching SHE values anorder of magnitudelarger than that reported for any oxide. Additionally, we derive three other design principles for enhancing SHE. Our findings bring deeper insight into the physics driving SHE and could help enhance and externally control SHE values.

Spin Hall Conductivity and Anomalous Hall Conductivity in Full Heusler compounds

“…It shows very pronounced SHC in the energy window. Hybridizations of the two orbitals occurs at the W-point, which is in agreement with scenarios proposed by Jadaun et al [26] Therefore, as already commented by Kübler et al, the AHC does not only determined by the strength of atomic SOC, but also related to the details of the electronic structure, namely, the interactions of the atomic orbitals. From the data obtained so far, we cannot draw any conclusions of the principles to obtain large SHE in Heusler compounds, although the nodal lines are proposed as a character of the large SHC/AHC [15].…”

“…5 (a). We see that in the figure the maximum is likely to be achieved in the magnetic compounds with Y = Mn and also in the nonmagnetic } orbitals due to the SOC is the main underlying mechanism for the anomalous velocity in TMO [26]. d xy and d x 2 −y 2 orbitals belong to the different representation basis of the cubic group.…”

Modulation of Spin–Orbit Torque from SrRuO3 by Epitaxial‐Strain‐Induced Octahedral Rotation

“…First, the band structure of SrRuO 3 determines its intrinsic SHC, which is strongly influenced by the octahedral crystal field. [ 27–30 ] Second, the octahedral rotation may alter the local inversion symmetry, which has been demonstrated to be crucial for SOT generation. [ 12,31,32 ] Therefore, tuning the octahedral rotation represents a distinguished means of modulating SOT since it potentially allows external control of the intrinsic SHC.…”

“…This is consistent with the previous theoretical studies. [ 15,30 ] It has been predicted [ 30 ] that in a transition metal oxide like SrRuO 3 , the distortion of the octahedral crystal field due to octahedral rotation splits the e g and t 2g manifolds into sub‐bands, where an overlap between the manifolds or sub‐bands is supported by the effect of spin–orbit coupling. This counters the dampening effect of a strong crystal field on the spin Hall effect and results in substantially enhanced intrinsic SHC.…”

Spin-orbit torque generation in NiFe/IrO2 bilayers

“…The large effective spin Hall angle of IrO2 not only support the significance of 5d electrons in the SOT generation but demonstrate the possibility of efficient room-temperature spintronics based on 5d transition-metal oxides. Towards further understanding of the charge to spin current conversion, our findings will inspire future works on the other Ir oxides with a variety of the electronic structures; significant enhancement of SHE is indeed predicted based on the unique electronic structures of Ir oxides [50,51].…”